1. Field of the Invention
The present invention relates generally to electrical switching apparatus and, more particularly, to an auxiliary switch actuator mechanism for a circuit breaker. The invention also relates to circuit breakers employing an auxiliary switch actuator mechanism.
2. Background Information
Circuit breakers having auxiliary switches are generally old and well known in the art. Typically, the auxiliary switch is electrically connected with a circuit including a status indicator (e.g., an audible alarm, such as a bell, or a visual indicator, such as a light) for providing a remote indication of the condition of the circuit breaker. Some auxiliary switches provide different outputs for each of the three general circuit breaker conditions, OFF, ON, and tripped. Other auxiliary switches only provide an indication when the circuit breaker has tripped.
The design and configuration of auxiliary switches, which will be discussed in further detail herein, is substantially uniform and unchanging throughout the industry. While this is advantageous from the standpoint of establishing an industry standard, it is disadvantageous in that there is a lack of variation in switch design making it difficult to accommodate the differing requirements of various switching applications. For example, the microswitch or internal contacts of most known auxiliary switches are not actuated unless the circuit breaker is tripped. In certain applications, it is desirable to have the opposite situation, with the microswitch being activated until the breaker trips. Known auxiliary switch designs, alone, cannot accommodate these circumstances. Therefore, in order to achieve the desired auxiliary switch operation, it has been necessary to make modifications to the internal components of the circuit breaker. Accordingly, known circuit breaker designs have begun to incorporate auxiliary switch actuating mechanisms.
For example, U.S. Pat. No. 4,707,674 discloses a representative auxiliary switch actuator mechanism of the type shown in FIGS. 1 and 2. FIG. 1 shows a circuit breaker 2 and the auxiliary switch actuating mechanism 4 therefor. FIG. 2 shows certain elements of the actuating mechanism 4 in greater detail.
Generally, when the circuit breaker handle 6 is moved from the OFF position (not shown) to the ON position, as shown in FIG. 1, a breaker mechanism 8 acts on a movable contact arm 10 causing it to pivot about the pivot axis defined by mounting pin 12. In response, a movable contact 14 on the contact arm 10 engages a fixed contact 16, as shown. As the contact arm 10 pivots, the bottom surface 18 thereof engages actuator arm 20 causing actuator member 22 to pivot about the axis defined by mounting pin 24, against a spring-bias exerted by an internal contact (not shown) of auxiliary switch 26. The internal contact (not shown) is coupled to movable pin 28 and is actuated thereby. As the actuator member 22 continues to move, the end of it opposite pin 24 slides past shoulder 30 of locking member 32 (see also FIG. 2).
A spring 34 biases the locking member 32 counterclockwise (with respect to FIG. 1) about pin 12, which results in shoulder 30 overlapping the upper surface 36 of base plate 38 at this location, thereby forming a stop which prevents movement of actuator member 22. Additionally, finger 40 engages the back edge 42 (FIG. 2) of slot 44 (FIG. 2) in actuator member 22 thus limiting the counterclockwise motion of locking member 32. In this manner, the auxiliary switch 26 is held in the actuated position until the shoulder 30 of locking arm 46 is moved out of engagement with the actuator member 22.
Typically, the auxiliary switch 26 has three contact terminals including a common (“C”) terminal 48 proximate the line side of the circuit breaker 2, a normally closed (“NC”) terminal 50 proximate the opposite or load side of the circuit breaker 2, and a generally central normally open (“NO”) terminal 52. Current flows through the auxiliary switch 26 between the C terminal 48 and one of the NC and NO terminals 50,52. When the circuit breaker 2 is turned ON (FIG. 1), the circuit through the main breaker contacts 14,16 is closed and the actuator member 22 sets the auxiliary switch 26, as previously discussed. This represents the actuated state of the auxiliary switch 26 in which the circuit between the C and NO terminals 48,52 is closed. However, as disclosed in U.S. Pat. No. 4,707,674, the auxiliary switch 26 could be operated in the opposite manner (e.g., with the C terminal 48 being electrically connected to the NC terminal 50 when the main breaker contacts 14,16 are closed).
When the circuit breaker handle 6 is manually moved between the ON and OFF positions, a sear pin 54 engages the link members of the breaker mechanism 8 in order to prevent them from collapsing. The breaker mechanism 8 remains engaged and locked by the sear pin 54 as the handle 6 pivots counterclockwise (with respect to FIG. 1) from the ON position (FIG. 1) toward the OFF position (not shown). In other words, when the circuit breaker handle 6 is manually operated, the sear pin 54 follows a first path of travel which avoids contact with second arm 56 of locking member 32. As movable contact arm 10 pivots upward, counterclockwise about pin 12, movable contact 14 disengages fixed contact 16 in order to open the main circuit. This also releases the force exerted by moveable contact arm 10 on pin 28 of auxiliary switch 26 through actuator arm 20 of actuator member 22. Normally, in the absence of any restraint on actuator member 22, the bias on moveable pin 28 exerted by the internal spring (not shown) of the auxiliary switch 26 would cause the internal contact to be returned to the NC position. However, this is prevented by the action of locking member 32. Specifically, the shoulder 30 of arm 46 acts as a stop against base plate 38 of actuator member 22 in order to restrain the bias thereof caused by the auxiliary switch internal contact (not shown) through movable pin 28 (best shown in FIG. 1). Therefore, when the circuit breaker 2 is manually opened, the auxiliary switch 26 remains actuated, with the NO contact closed.
Conversely, when a trip condition causes the circuit breaker 2 to trip, the armature 58 (FIG. 1) pivots causing the sear pin 54 to pivot and release allowing it to collapse the linkage of breaker mechanism 8 thereby separating contacts 14,16 and opening the main circuit. This collapse releases the sear pin 54 causing it to move in a second path of travel in which it contacts the second arm 56 of locking member 32. As the sear pin 54 continues to move, it causes locking member 32 to rotate clockwise (with respect to FIG. 1) about pin 12, against the spring-bias generated by spring 34. Then, shoulder 30 disengages base plate 38, releasing the actuator member 22 and allowing movable pin 28 of the auxiliary switch 26 to move outwardly in accordance with the bias provided by internal spring contact (not shown) in order that the auxiliary switch 26 switches from the actuated state to the non-actuated state. Therefore, an alarm circuit (not shown) connected between the C and NC terminals 48,50 of the auxiliary switch 26, is closed.
Despite the foregoing advancements in the art, significant disadvantageous remain. For example, the aforementioned auxiliary switch actuating mechanism is complex, requires numerous separate components and demands that all of the components interact precisely in order to function properly. For example, the shoulder and slot features and multiple interacting components previously discussed, could slip, become misaligned, or otherwise fail to interact correctly. Additionally, such an actuating mechanism requires the auxiliary switch to be modified, for example, to include a molded projection (FIGS. 1 and 2) with openings to receive mounting pin 24 about which actuator member 22 pivots.
There is a need, therefore, for a simplified auxiliary switch actuating mechanism which is capable of reversing the operation of a standard auxiliary switch, without requiring the auxiliary switch to be modified.
There is, therefore, room for improvement in auxiliary switch actuating mechanisms and in circuit breakers employing an auxiliary switch actuating mechanism.